The invention relates to an apparatus for controlling the operational current for electromagnetic switching systems, especially of electromagnetic fuel injection valves associated with an internal combustion engine. In operation, the fuel injection valves receive control pulses from a fuel injection control system, and the duration of the pulses is determined on the basis of the air flow rate of the engine and the prevailing rotational speed (rpm).
In general, electromagnetic switching systems, especially relays, control coils, etc., only operate when the control signal reaches a certain level. It is thus of advantage to operate such systems with relatively heavy switching currents so as to prevent any delay in operation. On the other hand, such heavy currents result in a considerable load on the system and on the output circuit when the stationary switching state is reached and maintained. In addition to the heavy power losses, the current-carrying portion of the switching system stores a substantial amount of energy which may become a disturbing factor at the time of turn-off. A further disadvantage of using a heavy turn-on current is to generate a substantial delay when the system, especially a control valve, is turned off.